Seismology is used for exploration, archaeological studies, and engineering projects that require geological information. Exploration seismology techniques are used widely in the oil and gas industry in the exploration to identify prospects and types of geologic formations. In order to apply a seismic investigation of a geological area, the seismic data shall be acquired based on an optimal seismic acquisition system that defines the source and receiver locations for all the shots. With the seismic data as well as seismic processing and imaging techniques are deployed to generate subsurface images of the geologic area for interpretation.
Acquisition illumination is widely used to evaluate the acquisition system capability in acquiring the reflection information for subsurface structures. It also can be used to compensate the seismic image in order to minimize the effect of unbalanced illumination on subsurface structures. Acquisition illumination is a combination of effects from source and receiver locations for all the shots, subsurface structures of the model, and model properties. The calculation of acquisition illumination requires calculating both the source-side illumination and the receiver-side illumination for all the shots in the acquisition system, which typically involves a large amount of computations for production applications.
Reverse Time Migration (RTM) is the most advanced seismic imaging method. It is widely used in seismic processing in oil and gas industry as a standard advanced imaging method. The basic concept of RTM includes three parts, which are 1) simulating the source propagation, i.e., propagating forwards in time; 2) back-propagating the receiver records, i.e., propagating backwards in time; and 3) applying cross-correlation image condition with source and receiver wavefields at each time step during the propagation. Since the simulation of source and receiver wave propagations and applying image condition require a large amount of numerical computation, RTM is a computationally intensive process.
Acquisition illumination can be used to further improve imaging quality output from RTM as a compensation for the acquisition and complex structure effect. In the implementation of RTM, the source-side wavefield for each shot will be calculated. The source-side wavefield can be used to generate source-side illumination by summing up all the source-side wavefields for all the time steps. However, there is no receiver-side wavefield calculated for each receiver in RTM processing so that RTM cannot output receiver-side illumination. Accordingly, acquisition illumination during RTM processing still needs improvement. The current disclosure provides solutions to solve this issue.